Absolute configuration of tert-butyl-1-(2-methylnaphthyl)phosphine oxide.

Wang F, Wang Y, Polavarapu PL, Li T, Drabowicz J, Pietrusiewicz KM, Zygo K
J Org Chem. 2002 67 (18): 6539-41

PMID: 12201778 · DOI:10.1021/jo025908h

The enantiomers of tert-butyl-1-(2-methylnaphthyl)phosphine oxide 1 have been separated using a homemade HPLC column and an analytical gradient system. Vibrational absorption and circular dichroism spectra for both enantiomers have been measured in CD2Cl2 and CH2Cl2 solutions in the 2000-900 cm(-1) region. The fully relaxed potential energy surface of (S)-tert-butyl-1-(2-methylnaphthyl)phosphine oxide, obtained using the B3LYP functional with a 6-31G basis set, indicated two stable conformers with their populations in a approximately 2:1 ratio. The vibrational absorption and VCD spectra are predicted for these two conformers using the B3LYP functional with a 6-31G basis set. The comparison of predicted and experimental spectra indicated that (+)-tert-butyl-1-(2-methylnaphthyl)phosphine oxide is in the (S)-configuration. This assignment is supported by the ab initio prediction of positive optical rotation for the most stable conformer with an (S)-configuration and the nonequivalence sense of the tert-butyl group chemical shift observed in the 1H NMR spectrum of this enantiomer measured in the presence of (+)-(S)-mandelic acid as a chiral solvating agent.

MeSH Terms (9)

Chromatography, High Pressure Liquid Circular Dichroism Magnetic Resonance Spectroscopy Mandelic Acids Molecular Conformation Molecular Structure Naphthalenes Organophosphorus Compounds Stereoisomerism

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